Clipboard crash Fix

Currently `SparkleShare.SparkleController.CopyToClipboard()` may encounter a `System.Runtime.InteropServices.COMException` due to multiple process accessing the non thread safe Windows clipboard. This exception occurs in the untouchable Windows API and may occur at any time throughout the lifetime of SparkleShare, but is unlikely. (http://www.infragistics.com/community/forums/t/35379.aspx) 

This issue has been fixed by Microsoft in .Net 4.5 by implementing attempts multiple times. Since we are running Mono this fix has not propagated yet. 

I prompt to catch the exception and only log to debug about the error as there is no standard action to handle this issue and as a framework fix has been created. At the very least SparkleShare will not crash.